Tap and process of making the same.



L/ze for;

2 SHEETS-SHEET l.

PATENTED OCT. 2, 1906. HARTNESS.v

SS 0F MAKING THE SAME.

ATION FILED rBB.1a.19o4.

AND

TAP

UNITED sT-ATEs `PATENT OFFICE.

TAP AND PROCESS OF MAKING THE SAMEI Specification of Letters Patent.

Patented Oct. 2, 1906.

Application filed February 18, 1904. Serial No. 194.170.

To aZZ whom it may concern/.-

Be it known that I, JAMES HARTNEss, of Springfield, in the county of Windsor and State of Vermont, have invented certain new and useful Improvements in Ta s and Processes of Making the Same, of W ich the following is a specification.

This invention has relation to taps and to methods of manufacturing them.

The obj ect of the invention-is the production of a finished tap having an exact predetermined diameter and an accurate lead-fi. e., the exact number of accurately-spaced teeth in the given length of the tap and without the inaccuracies which have heretofore re- .sulted from the previous methods of produclng taps.

Heretofore it has been customary to first cut or otherwise form upon a tap-blank teeth of substantially the exact diameter desired and of a lead sufficiently greater or less than the lead of the desired finished article to compensate for the ex ansion or contraction of t e particular stee used in its manufacture..` After forming the tap-blank as nearly as possible like the desired finished article it has been customary to then subject the blank to the hardening rocess. The expansion and contraction o the steel are not sufficlently uniform, however, to make the rocess as described reliable, since it resu ts in bending the tap or making it crooked, in destroying the accuracy of the lead and the diameter of the tap, and in distorting the shape of the teeth for fine work. Such taps are 1nefficient and untrustworthy. According to the present invention these above-noted imperfections and inaccuracies are entirely obviated and prevented by first forming the blank with teeth' having an excess of material or stock on their sides and tops sufficient to compensate for lateral distortion of the teeth ,and for the curvature or crookedness of the tap, hardening the blanks, and then glrinding off the surplus or excess material om the teeth to produce a perfect lead and the exact predetermined diameter. To aid in the grinding operation, some ofthe teeth are formed with vclearances at their bases for the reception of the grinding-tool, these clearances being so located that they do not interfere or effect the result desired to be produced by the tap intapping a hole. The result of my process is a straight and true tap with an accurate lead and an exact diameter and with clearances at the bases of the teeth, or some of them, as hereinafterdescribed.

Referring to the accompanying drawings, Figure 1 represents a tap in process of construction, grinding-tools being illustrated as in the act of removing the excess or surplus material from the sides of some of the teeth. Fig. 2 represents an end view of the tap. 3 represents an enlarged section on the line 3 3 of Fig. 2. Fig. 4 represents an enlarged section on the line 4 4 of Fig. 2. Figs. 5 and 6 represent enlarged sections through the teeth of another tap embodying the invention. Figs. 7 and 8 are similar sections throu h the teeth of still another form of tap embo ying the linvention. Figs. 9 and 10 represent sections through the teeth of a tap embodyin the invention.

It will e understood that the invention may be practiced or embodied in ways and devices other than those illustrated and described and, further, that the terms and phraseology are employed for the purpose of description and not of limitation.

In carrying out the invention a blank a, of relatively soft metal, is produced, which is cylindrical in form. U on this blank are formed threads by a ro ling, cutting, or milling process, the blank having the usual shank b, squared, as at b. longitudinally milled or grooved to divide the threads into a plurality of series of teeth, there being usuali four series c d ef, respectively, although t e number may be varied as desired. All of the teeth approximate in a general way the shape of the finished teeth; but they are initially formed on their sides one l(or both) and tops with sufficient stock or excess material to permit of a considerable distortion or bodily displacement of the teeth in the hardening process without their entirely leaving the spaces to be occupied by the finished teeth. The surplus or excess material is graphically represented as lying between the full and dotted lines in the various figures illustrating the-teeth on an enlarged scale. The blank after being thus initially formed is subjected to the usual har- The blank maybe then i IOC I the hardening process each tooth is ground to remove the surplus or excess material to bring the tap to the exact predetermined diameter, with the teeth accurately spaced and with all of the teeth in such condition as to perform their work in tapping a hole without maccuracies.

In order that the teeth may be ground `to the desired size and lead, some ofthe teeth, as stated, are formed with clearances at their bases for the grinding-tool, which is indicated at g as in the form of an emery-wheel. These clearances may be variously formed and located. In Fig. 3, for instance, the series c is illustrated, and in Fig. 4 the series d. The teeth c', c, and c3 are-each formed with excess material y z on their sides and tops. Each yoi" the teeth has upon its left side a clearance p, which extends below the base-line of the teeth, said base-line being indicated by the dotted line AA in all the lfigures. The clearance p is suflicient in size to permit of the entrance of the edge or rim of the emery-Wheel g and permit the grinding of the side 'y' of the tooth from its crown or top to the base-line. The series d^ d2 da, which follow successively the teeth c c2 c3, are likewise 'formed withexcess material; but it Will be observed that in these teeth the clearance p is formed in the sides y of the teeth to permit ofthe grinding of the side from its crown to or below its base-line. The sides of the teeth c c2 and the sides y of the teeth d d2, &c., are ground simply from the crown to the upper end of the clearance, and consequently there is no necessity for the formation of a clearance in this casein the sides y of the teeth d d2 or in the sides of the teeth c c. It will be understood that the series of teeth e is formed similarly to those at c and that the series f is formed similarly to the series d.

When a tap constructed in this manner is used, the successive cutting edges on thev teeth operate to remove thev material in the work left by reason of the formation of the clearances. It will be understood that these clearances may be otherwise located, as prevviously indicated. For instance, in Figs. 5

and 6, which illustrate the series of teeth c d, respectively,y each of the series c is formed with alternate teeth missing-that is to say, it has the teeth c c3 c5 or d/ d3 d5, with the teeth c2 c4 c and d2 d4 d omitted. case the clearances p are formed below the base-line A A.

In Figs. 7 and 8, which illustrate a series of teeth c and d, instead of omitting the alternate teeth c2 c4 c and d2 d4 d the clearances p In this areformed in the sides of said alternate teeth and extend below the base-line of the remain- 6 5 ing teeth. In both forms ofthe tap shown in Figs. 5 and 6 and 7 and 8 each series of teeth is formed to remove from the work the material left by the preceding series of teeth. n

In Figs. 9 and 10 a construction is illustrated in which in each series of teeth only one side and the crown of the tooth are adapted to operate upon the work. In these two figures the full lines indicate the finished teeth, the dotted lines indicating the excess material left upon the tooth rior to the grinding operation and the ot-and-dash lines indicating the extent of the cut formed in the work by the successive series of teeth.

It will be observed that in Fig. 9, for instance, th'e tooth c has a cutting edge y and the crown z', the excess material y and 2 being ground away in accordance with the previously-described process. The other side x2 of the tooth is initially formed so as to leave a clearance between it and the work in order that the clearance p may be formed at the bases of the sides y. The cutting edges of each tooth are, ,as stated, on the sides y and the crown z. In the succeeding series of teeth d the tooth d has its side y2 cut away for the formation of the clearance p at the base of the cutting edge or side on the next tooth ofthe same series. AIn the'operation of rial left in the work by the side x2 of the tooth c is removed by the cutting edge of the next succeeding tooth of the second series. The teeth in Figs. 9 and 10 are illustrated as being at the front end of the tap, with their crowns beveled in the usual manner. The teeth in all of these igures are similar in that there are clearances formed at the base of some of the teeth and with the teeth so formed that the material left by the clearances is removed by the successiveseries of teeth. The teeth are further similar in that they are ground to an exact size, diameter. and lea :1, so as to cut or form threads in the work with unvarying accuracy.

'Having thus explalned the nature of the invention and described a way of constructing and using the same, although without attempting to set forth all of the'forms in which it may be made or all of the modes of its use, I declare that what I claim is 1. The herein-described process of producing taps, which consists in forming a tapblank With excess material on the teeth, and with clearances Within the base-line of the teeth to receive an abrading-tool, hardening the blank, and removing by abrasion the excess material on said teeth, to reduce them to a predetermined size and lead.

2. The herein-described process of producing tapsv which consists in forming a tap# IIO , blank with excess 'material on the crowns and f quent hardening ofthe blank, and clearances sides of the teeth, and With clearances Within Within the base-lines of some of the teeth to the base-line ofthe teeth to receive an abradreceive an abrading-tool. ing-tool hardening said blank, and by abra- In testimony'whereof I have affixed my 5 sion removingl the excss mlaterialdfromhthe signature in presence of tWo Witnesses.

crowns and si es o sai teet to re uce t em 1 to a predetermined diameter, size and lead. JAME HARTNESS' 3. A tap-blank of relatively soft metal hav- Witnesses: ing an excess of material on its teeth sufri- D. S. BROWNELL, 10k cient to compensate for distortion in a subse A. N. HOWE. 

